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Ross Haberman, a hedge fund manager from Manhattan, has enjoyed a swanky duplex on Park Avenue for a pittance -- $380 a month (yes, we wrote that correctly) – for more than a decade. But now some of his family members who have a stake in the building want to raise the rent.

A one-bedroom apartment at 737 Park Ave. could go for $8,000 or more, reports the Daily News. Haberman's grandfather owned the 20-story building, however, and upon his death, granted his six grandchildren lifetime rentals there for just $300 a month.

Three of the grandkids have moved out, but Haberman, who moved into the building in 1991, wants to stay at the same price. So he filed a lawsuit. The suit, filed in Manhattan Supreme Court, argues Haberman's cousins, both board members in the building, strove to raise rent for family pads "to a rate closer to the fair market value," reports the News.

Fair market value would certainly entail a greater spike than the meager $80 he had to pay on top of his $300 a month when he and his wife combined two apartments a decade ago, according to the paper. A few months ago, a comparable apartment in the building went for a staggering $8,500 a month, reports Streeteasy.com. That could mean more than a 2000 percent increase for Haberman per month.

Other tenants in the building are stupefied by Haberman's good fortune.

"$380? Wow, that's a deal," Richard Foxman told the News. "People would go nuts for a deal like that. I could understand him suing to keep it from going up exponentially."